The present invention relates to a method of dividing a semiconductor wafer having a plurality of circuits (chips) formed on the surface thereof, the circuits (chips) being sectioned by streets or by streets with a metal layer formed thereon, into individual chips.
For example, in the production of a semiconductor device, a surface of a substantially disk-like semiconductor wafer is sectioned into a plurality of rectangular regions by cutting lines called xe2x80x9cstreetsxe2x80x9d arranged in a lattice form and a predetermined circuit (chip) is formed in each of the rectangular regions. In the semiconductor wafer, further, a pattern formed from a metal such as aluminum or copper, that is called xe2x80x9cTEG (Test Element Group)xe2x80x9d, is provided for testing the characteristic properties of each circuit (chip), and this metal layer is formed on the surface of each street in some cases. The plurality of rectangular regions each having a circuit (chip) formed therein are cut and separated from one another to form a so-called semiconductor chip. The semiconductor wafer is cut by a precision cutting machine that is generally called xe2x80x9cdicing machinexe2x80x9d. In this dicing machine, the semiconductor wafer is cut along the streets formed on the surface of the semiconductor wafer with a rotary blade that has a thickness of about 20 xcexcm and rotates at a high speed, thereby to divide it into chips. As another means of dividing the semiconductor wafer, cutting by using a laser beam or a point scriber for cutting glass is also now on trial.
Since the division of the semiconductor wafer by the dicing machine is thus carried out in such a manner that cutting grooves are formed by using a rotary blade rotating at a high speed while impact force is given to the streets to gradually break them, a plurality of chippings as fine as several microns are formed on both sides of each cutting groove. Therefore, as chips to be formed on the semiconductor wafer must be arranged in a range beyond the reach of chippings produced by cutting, each street needs to have a width of about 50 xcexcm when a semiconductor wafer is cut by the dicing machine. To enhance the productivity of semiconductor chips, however, how many chips can be formed on one semiconductor wafer is a very important issue and hence, how narrow the width of each street where the chips are not formed can be made is the key to this end. Meanwhile, cutting by a point scriber or laser beam is not always satisfactory from a productivity standpoint because a yield of the product is lowered due to breakage or the like though the cutting width is small.
When the semiconductor wafer having streets of which the surface has a metal layer formed thereon is cut by a rotary blade, whiskered burrs tend to generate on both sides of a cutting groove because the metal layer is soft, sticky and easily deformed. The burr causes such undesirable problems as occurrence of a short-circuit between laminated layers or between bonding wires, scratches, or a damaged adjacent circuit when it falls off.
It is a first object of the present invention to provide a method of dividing a semiconductor wafer, which can narrow the width of the streets and hence, can enhance productivity with a good product yield.
It is a second object of the present invention to provide a method of dividing a semiconductor wafer, which is capable of dividing a semiconductor wafer having streets of which the surface has a metal layer formed thereon, without generating any burr.
To attain the above first object, according to the present invention, there is provided a method of dividing a semiconductor wafer of which the surface has a plurality of chips sectioned by streets, into individual chips, characterized in that the method comprises:
a scribing step in which division guide lines are formed by drawing scribed lines along the streets on the surface of the semiconductor wafer;
a tape sticking step in which a tape is stuck onto the surface having the division guide lines formed thereon, of the semiconductor wafer; and
a back surface cutting step in which cutting grooves are formed in the back surface, to which the tape has been stuck, of the semiconductor wafer such that a bit of uncut portions are left along the division guide lines, and:
by the formation of the cutting grooves, the uncut portions are completely separated with the aid of the division guide lines to divide the semiconductor wafer into individual chips.
The division guide lines formed in the scribing step are formed by a scriber and the cutting grooves formed in the back surface cutting step are formed by a rotary blade.
To attain the second object, according to the present invention, there is provided a method of dividing a semiconductor wafer, of which the surface has a plurality of chips sectioned by streets with a metal layer formed thereon, into individual chips, characterized in that the method comprises:
a scribing step in which division guide lines are formed by drawing scribed lines along streets on the surface of the semiconductor wafer;
a tape sticking step in which a tape is stuck onto the surface having the division guide lines formed thereon, of the semiconductor wafer; and
a back surface cutting step in which cutting grooves are formed in the back surface, to which the tape is stuck, of the semiconductor wafer such that a bit of uncut portions are left along the division guide lines, and:
by the formation of the cutting grooves, the uncut portions are completely separated with the aid of the division guide lines to divide the semiconductor wafer into individual chips.
The division guide lines formed in the scribing step are formed by breaking the metal layer formed on the streets by a roller scriber and the cutting grooves formed in the back surface cutting step are formed by a rotary blade.